package com.zmx.gateway.utils;

import lombok.Data;
import lombok.ToString;
import lombok.extern.slf4j.Slf4j;

import java.io.Serializable;

/**
 * @Description: 简易版对整数进行过滤、判断是否已存在
 * @ClassName: SimpleBitMapUtil
 * @Author zhaomxr
 * @Date 2021-12-02 10:30
 */
@Slf4j
@Data
@ToString
public class SimpleBitMap implements Serializable {

    /**
     * 存储数据 byte数组
     */
    private byte[] bytes;

    /**
     * 数组最大容量
     */
    private int capacity;

    public SimpleBitMap() {
    }

    public SimpleBitMap(int capacity) {
        this.capacity = capacity;
        bytes = new byte[(this.capacity >> 3) + 1];
    }

    /**
     * 新增元素
     * @param element
     */
    public void add(int element) {
        //当前元素所在数组下标 element/8
        int code = element >> 3;

        //当前元素在byte中bit位置 element%8
        int position = element & 0x07;

        //将1左移position位后，与原有数据做 | 或运算，指定位置值就变为1
        bytes[code] |= 1 << position;
    }

    /**
     * 判断当前元素是否已在BitMap中存在
     * @param element
     * @return
     */
    public boolean contain(int element) {
        //当前元素所在数组下标 element/8
        int code = element >> 3;

        //当前元素在byte中bit位置 element%8
        int position = element & 0x07;

        return (bytes[code] & (1 << position)) != 0;
    }

    /**
     * 清除当前元素
     * @param element
     */
    public void clear(int element) {
        //当前元素所在数组下标 element/8
        int code = element >> 3;

        //当前元素在byte中bit位置 element%8
        int position = element & 0x07;

        //将1左移position位，取反，此时就是0，在与原有元素进行&运算，此位置元素清除为0
        bytes[code] &= ~(1 << position);
    }

    public static void main(String[] args) {
        long addStart = System.currentTimeMillis();
        SimpleBitMap simpleBitMap = new SimpleBitMap(1000000);
        int[] elements = new int[]{1, 3, 5, 6, 12, 4, 16, 12, 56, 34, 3, 12, 44, 22};
        for (int i = 0; i < 1000000; i++) {
            simpleBitMap.add(i);
        }
        System.out.println("存储元素用时：" + ""+(System.currentTimeMillis() - addStart));
        System.out.println("----------------over----------------");

        System.out.println("BitMap占用内存：" + simpleBitMap.bytes.length / 1024 +"KB");
        System.out.println("BitMap占用内存：" + simpleBitMap.bytes.length / (1024 * 1024) +"MB");
        System.out.println("BitMap占用内存：" + simpleBitMap.bytes.length / (1024 * 1024 * 1024) +"MB");


        long start = System.currentTimeMillis();
        System.out.println(simpleBitMap.contain(3));
        System.out.println(simpleBitMap.contain(500000));
        System.out.println(simpleBitMap.contain(702441));
        System.out.println("查询元素用时：" + ""+(System.currentTimeMillis() - start));

        System.out.println("--------------------------------");
        simpleBitMap.clear(3);
        System.out.println(simpleBitMap.contain(3));
    }
}
